Pole-piece for dynamo-electric machines



UNITED STATES PATENT OFFICE.

ELII-IU THOMSON, OF SVAMPSCOTT, ASSIGNOR TO THE THOMSON-HOUSTON ELECTRIC COMPANY, OF BOSTON, MASSACHUSETTS.

POLE-PIECE FOR DYNAMO-ELECTRIC MACHINES.

SPECIFICATION forming part of Letters Patent No. 498,827, dated May 30, 1893.

APPHGR'GOII flied August 26, 1892. Serial No. 444,240. (No model.)

To all whom t may concern:

Be it known that I, ELIHU THOMSON, a citizen of the United States, residing at Swampscott, county of Essex, State of Massachusetts, have invented certain new and useful Improvements in the Manufacture of Dynamo-Electric Machines, of which the followingr is a specification.

The present invention relates to means for 1o dividing the projecting poles or pole faces of dynamo electric machines or motors,particu larly of alternating current dynamos in which by the action of the armature, eddy currents may be set up which Waste power in the pole I5 faces. The construction is more particularly adapted to such armatures as are provided with projections of iron running near to the pole faces, or provided with a discontinuous exterior of iron. It has been customary to 2o construct pole faces of laminas or laminated iron in such cases. Inasmuch, however, as the actions which are to be guarded against are not, in many cases, so important as to demand an entirely laminated structure, and

z5 inasmuch further, as the disturbing actions do not extend back into the pole face to any great extent in many cases my present invention is a cheap means Ior obtaining a saving of power depending upon slotting of 3o the pole faces, which is sometimes done by mechanical cutting appliances. In my invention during the process of forming the pole pieces from either cast or wrought iron I produce the slots by proper molding. The

g 5 preferred Inode of producing the slots is shown in the accompanying drawings.

Figure l represents a piece of the pole, in the face of which are inserted heat resisting pieces of non-conducting material. Fig. 2 is 4o an end view of the same. Figs. 3 and 4 show slot-forming pieces of sheet metal. Figs. 5 and 6 are vertical and horizontal sections respectively of a molding flask for casting polepieces. Fig. 7 shows apole piece slotted, and

Fig. 8 a portion of an alternating dynamo field magnet with slotted pole pieces.

The divisions in the pole piece A may be open slots c, as shown in Figs. 3 and 7 or the slots may be filled with an insulating material B as in Figs. l and 4E. In Fig. 7 the slots 5o are cored out by inserting suitable cores in the mold C before casting. Or,the cores may consist of slabs of heat-resisting, non-conducting material B, such as baked clay, and the pole piece when cast, will retain these pieces in it, as shown in Fig. l.

I iind that one of the best means of introducing the insulating substance for producing slots in the poles is by taking a piece D of sheet iron and bending it into a U form, 6o as in Fig. 3, so as to leave a little space between the two sides, inserting this into the mold and casting around it, in which case the metal lits itself and welds itself to the piece of sheet iron which then becomes practically a part of the structure, and maybe machined or cut as is the other part. Vhere the temperature is so low as not to cause a welding, the pieces may be knocked out afterward, but in eithercase they form the slot required. 7o

It is preferable in some cases to introduce between the folded piece of metal a slab or sheet of insulating material B, which may be asbestus or clay, or a loose slab of any such substance. The piece l) in Fig. 4c is intro- 75 duced into the flask or mold as in Figs. 5 and G.

lVhat I claim as new, and desire to secure by Letters Patent, is-

l. A cast metal pole piece for a dynamo, So having in its face anumber of slots, each containing an insulating piece of heat resisting material, substantially as described.

2. A cast metal pole piece for a dynamo, having in its face a number of U-shaped pieces of sheet metal, substantially as described.

3. A cast metal pole piece for a dynamo, having embedded in its face a number of U- shaped pieces of sheet metal, each having a 9c slab of insulating material infolded in it, substantially as described.

In witness whereof I have hereunto set my hand this 22d day of August, 1892.

ELIHU THOMSON.

Witnesses:

JOHN W. GIBBONEY, BENJAMIN B. HULL. 

